Water Underfloor Heating over Existing Floors

If you have a retrofit project or need to make underfloor heating work for floors you already have, then an overlay system might be the ideal solution. Overlay systems are one of the most underrated types of water underfloor heating system available today. They are a great option for both new builds and existing properties, but are most popular as retrofit systems. Too many people incorrectly assume that unless they can accommodate an in-screed installation, then they cannot install water underfloor heating. This is simply not true. Overlay systems are versatile and almost universal to every type of property. They don’t require the floor to be dug out and are simply laid down onto the existing floor.

The existing floor is best prepared by covering with a shallow self levelling screed to give a perfectly level surface. The boards are then bonded to the floor and the pipes inserted into the grooves. Depending on the flooring you wish to lay down will determine how the surface of the boards are finished. Overlay systems are more efficient and effective then joist systems, and has the faster response out of all three system. The only downside to them is that they can be expensive and, most importantly, they will raise the floor height, but only up to 25mm. If you want to install water underfloor heating in your home and can accommodate the floor height increase, the overlay system is by far your best choice.

Pro Tip: Pick one of the 3 different finishing methods for water underfloor heating overlay systems – great for retrofitting – for your floor…

Wet Underfloor Heating – Under wood	Wet Underfloor Heating – Under carpet	Wet Underfloor Heating – Under tiles
The overlay board is bonded to the floor using a specialist non-solvent based adhesive. The pipe is pushed into the omega shaped grooves for a solid hold. Once the pipes have been pressure tested, the flooring can be laid. Cover with a 3mm breathable underlay before laying the flooring. Lay the flooring as a floating floor. The system can be turned on immediately with no drying time to consider. PRO TIP! If the flooring isn’t to be laid straight away, cover the overlay boards with some ply sheets to protect them from on-site foot traffic!	The overlay board is bonded to the floor using a specialist non-solvent based adhesive. The pipe is pushed into the omega shaped grooves for a solid hold. Once the pipes have been pressure tested, the flooring can be laid. Prepare the aluminium surface with a primer. Once dry, cover the surface with a 5-6mm quick dry self levelling screed. This evens out the feel of the grooves underfoot through the carpet. Lay the underlay and carpet as normal. PRO TIP! To get the best performance out of the system, do not exceed 2 tog rating carpet and underlay combined!	The overlay board is bonded to the floor using a specialist non-solvent based adhesive. The pipe is pushed into the omega shaped grooves for a solid hold. Once the pipes have been pressure tested, the flooring can be laid. Prepare the aluminium surface with a primer. Bond the tiles straight onto the boards using a flexible S2 adhesive. PRO TIP! Porcelain tiles work exceptionally well over this system for the highest output- up to 150w/sqm!

Which kit should you choose?
Now you have decided on your floor construction and learnt about the different fixing methods, is your project for a singe room or multiple rooms?

Single Room System > Materials to heat one room controlled by one thermostat

Multi Room System > Materials to heat multiple rooms, controlled by a thermostat in each room

We only use high quality European standard Pert-Al-Pert pipe in all our water underfloor heating systems.

Our range of pert-al-pert pipe is manufactured to ISO9001 European standards ensuring a lifetime of outstanding performance & reliability.

Five layer 16mm pert-al-pert pipe is used in all of our warm water underfloor heating kits and offers unrivaled suitability for underfloor heating by combining the best elements of a plastic and metal pipe into one product.

The aluminium core provides strength and importantly acts as an oxygen barrier to stop the ingress of oxygen into the system causing premature wear (corrosion) to the manifold. The aluminium layer also makes the pipe form-stable, making it very easy to work with by eliminating spring back for easier installation.